1. Field of the Invention
The present invention relates to a trailer hitch configured to be provided on a rear part of a vehicle, and to a rear structure of a vehicle having the trailer hitch.
2. Discussion of the Related Art
Various structures for mounting a trailer hitch on a rear part of a vehicle have been proposed. The trailer hitch is a member for detachably linking a trailer to a vehicle by way of a joint provided at a front part of a trailer.
Japanese Kokai Publication 2006-44352, for example, discloses an embodiment for a rear structure of a vehicle having a trailer hitch. The rear structure will be explained by referring to FIGS. 15 and 16.
FIG. 15 is a schematic cross-section of a rear structure of a vehicle having a trailer hitch. Further, FIG. 16 is a cross section of FIG. 15 obtained by cutting the rear structure thereof at a line with arrows XVI.
In a rear structure of a vehicle, a pair of rear side members extends in a lengthwise direction of a vehicle. FIG. 15 shows that a rear side member 102 extends in a lengthwise direction of the vehicle and is provided on a bottom surface of a floor section of the vehicle. On the other hand, a cross member 110 extends in a widthwise direction of the vehicle. For the connection, a rear end of the rear side member 102 abuts against a front surface of the cross member 110.
As shown in FIG. 16, a reinforcement member 112 is provided between the rear side member 102 and the cross member 110. The reinforcement member 112 includes an overhang part 113 having an outer periphery 113a so that the reinforcement member 112 has a cross section in the form of a hat having inclined side wall extending approximately in a lengthwise direction of the vehicle. Thus, the cross member 110 and the reinforcement member 112 form a structure with a closed cross section.
The rear side member 102 has an inclined weld flange 103 extending in a lengthwise direction of the vehicle at the rear end of the rear side member 102.
The overhang part 113 of the reinforcement member 112 protrudes in a frontward direction of the vehicle, and fits into the weld flange 103. In this structural configuration, the weld flange 103 of the rear side member 102 is welded to the outer periphery 113a of the overhand part 113.
On the other hand, a trailer hitch 120 includes a hitch ball 121 and arms 123 provided at both the ends of a frame 122, as described in FIG. 15 by an imaginary line. Therein, the frame 122 extends in a widthwise direction of the vehicle and supports the hitch ball 121 thereon. Moreover, the arms 123 extend from the frame 122 in a frontward direction of the vehicle, and frontal upper parts 123a of the arms 123 are fastened (bolted) to a rear lateral part 102a of the rear side members 102 with bolts.
In the above described structure, it is possible to prevent the welded parts from being separated from each other when a lengthwise force of the vehicle is repeatedly applied to the rear side member 102 via the trailer hitch for attracting a trailer (not shown). This is because the extending direction in a connection surface (defined by welding the outer periphery 113a of the overhang part 113 to the weld flanges 103) extends approximately in parallel with the direction of shearing force applied to this section.
Accordingly, the strength of the connection between the rear side members 102 and the cross member 110 is improved, so as to resist the load applied from the trailer to the rear side member 102.
In addition to the structure of the trailer hitch 120 itself, the fastening of the front upper ends of the arms 123 to the rear lateral parts 102a of the rear side members 102 reinforces the rigidity of the rear parts of the rear side members 102 for a broad range.
However, in the above trailer hitch 120, the rigidity of the rear side member 102 is excessively improved. In other words, the excessive reinforcement restricts the rear side member 102 from compression deformation in an axial direction of the rear side member 102. Therefore, the rear side member 102, especially at the rear part thereof, would fail to efficiently absorb a load which could be applied to the trailer hitch 120 by a rear-end collision or the like. In particular, if the above structure is attached to a vehicle that has a short rear overhang, the rear side members have limited compression deformation. This makes it difficult for the reinforced rear side member to effectively absorb the load applied by a collision.